It is important that an HIV-1 vaccine induce a CD8 cellular immune response. It is also central that an induced immune response be present at mucosal sites. The mucosal sites are entry routes for HIV-1 as well as a site of significant viral replication. Therefore, a cellular immune response at the mucosa will be important to protect and clear virus from these susceptible sites. IL-15 is a key molecule involved in the homeostatic proliferation and maintenance of CD8 effector and memory cells. In a non-human primate model we found IL-15 enhanced the antigen specific CD8 and CD4 lymphocyte proliferation upon in vitro antigen stimulation. Of relevance we also identified that IL-15 primed for a mucosal immune response. Finally and most notable we have found in the macaque model that the animals that received SHIV DNA vaccines co-delivered with plasmid IL-15 suppressed SHIV89.6p viral replication significantly. We hypothesize that the IL-15 increased the potential proliferative capacity of CD8 lymphocytes both in periphery. We further hypothesize that this antigen specific immune response is mirrored in the mucosa. The goals of this grant are to determine the nature of the CD8 mucosal immune response and further delineate the peripheral response that is induced by co-delivering IL-15 with a DNA vaccine. We have four specific aims to accomplish our goal. AIM1 and AIM 2 will develop and subsequently apply a quantitative RT-PCR system to evaluate a set of genes that can define the biological activity of peripheral and mucosal antigen specific CD8 lymphocytes. AIM3 will investigate the proliferative capacity of the peripheral and mucosal CD8 lymphocytes induced by vaccination with and without co-delivery of plasmid IL-15. AIM4 will investigate the peripheral and mucosal cellular immune responses in control and vaccinated animals following SIV challenge.